Electrical circuit breaker



p 1970- J. 1.. GRATZMULLER v 3,531,609

I ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 e Sheets- Shet 1 Sept.29, 1970 GRATZMULL-ER 3,531,609

ELECTRICAL CIRCUITV'BREAKER Filed April 12, 1967 6 Sheets-Sheet 2 -FIG.2

Sept. 29, 1970 J. 1. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 6 Sheets -Sheet 3 Sept.29, 1970 J. L. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER I Filed April 12, 1967 6 Sheets-Sheet &

v I27 15246 I e 90 I 'iMliH S t. 29, 1910 J. L. GRATZMULLER 3,531,609

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 6 Sheets-Sheet 5 p 1970J. GRATZMULLER 3, 3 0

ELECTRICAL CIRCUIT BREAKER Filed April 12, 1967 e Sheets-Sheet s UnitedStates Patent O M 3,531,609 ELECTRICAL CIRCUIT BREAKER Jean LouisGratzmuller, 66 Boulevard Maurice Barres, Neuilly-sur-Seine,Hauts-de-Seine, France Filed Apr. 12, 1967, Ser. No. 630,303 Claimspriority, application France, Apr. 15, 1966,

Int. Cl. rionl 33/68 US. Cl. 200150 13 Claims ABSTRACT OF THE DISCLOSUREBRIEF SUMMARY OF THE INVENTION This invention relates to electricalcircuit breakers especially but not exclusively to circuit breakers foruse in high and very high voltage circuits.

An object of the invention is to operate the cut in the arc in adielectric medium consisting of a liquid under permanent pressure, as aresult of which, certain characteristics of the dielectric medium, suchas the extinguishing power and the dielectric rigidity are improvedwhich allows better performances in the breaking and/or a lessening ofthe volume of the dielectric and so of the apparatus.

A further object of the invention is to use the energy contained in theform of pressure in the dielectric liquid under pressure, thisconstantly available pressure being utilized to operate the movingcontact of the circuit breaker in the direction of separating thecontacts, i.e., for the release.

As a result, as soon as the moving contact is no longer held in theclosed position by the locking devices or the normal holding devices(mechanical, hydraulic, pneumatic, etc.) this contact is pulled andseparated from the fixed contact to produce the break.

The present invention is an electrical circuit breaker comprising acircuit interrupting chamber in which are arranged a fixed contact and amovable contact and which contains a liquid dielectric, resilient meansfor keeping said liquid dielectric under permanent pressure, a breakingpiston solid with the movable contact, a cylinder in which the pistonslides and communicating at the end turned towards the moving contactwith the circuit interrupting chambers, releasable interlocking devicesto bring and maintain selectively the movable contact against the fixedcontact in opposition to the pressure of the liquid dielectric exertedon the breaking piston.

Preferably the insulating liquid is a liquefied gas having a highdielectric strength, such as sulphur hexafiuoride SP Preferably also,the resilient means for maintaining the insulating under pressure, is apneumatic device such as a cushion of gas under pressure acting on thedielectric liquid directly or through a hydraulic line; alternatively,it is a mechanical device such as a spring pushing a piston whichcompresses the dielectric liquid of the circuit breaker.

According to certain preferred embodiments of the invention theresilient devices for maintaining pressure comprise a hydraulicaccumulator, the same accumulator being used, in certain cases as apressure source for con- 3,531,609 Patented Sept. 29, 1970 tinuouslymaintaining the insulating liquid under pressure and as a pressure forcontrollably moving the movable contact of the circuit breaker to closedposition against the action of the continuously maintained pressure.

In practice, there can be fitted to circuit breakers in accordance withthe invention, devices for controlling the pressure and the volume ofthe dielectric liquid as well as devices for compensating variations inpressure and volume arising, for example, from variations intemperature.

In a circuit breaker according to the invention, a very effectivedeionization of the medium is effected Where the arc sparks due to thepressurizing of the liquid dielectric. In addition, the pressureexisting in the dielectric acts against cavitation phenomena whichnormally arise as the moving contact withdraws. The deionization andanticavitation thus obtained due to the invention are all the moreelfective because of the high pressure of the liquid dielectric. Thisdeionization can be made even more effective by circulating dielectricunder pressure right at the heart of the arc, circulation producing ahydraulic blow and being very simply obtained in a circuit breakeraccording to the invention.

BRIEF DESCRIPTION OF THE DRAWING Embodiments of the present inventionwill now be described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 is a sectional view of a circuit breaker in which the resilientdevices for pressurising the dielectric are made up of a cushion of gasunder pressure acting directly on the free level of the dielectric;

FIGS. 2 and 3 represent in section two variations of the circuit breakerin which the resilient devices are made from a spring acting on a pistonwhich directly compresses the dielectric;

FIG. 4 is a partial sectional view of a circuit breaker similar to thoseof FIGS. 1, 2 and 3 but having in addition a hydraulic system forblowing the arc;

FIGS. 5 and 6 are partial sectional views of circuit breakers similar tothose of FIGS. 1 to 4 but including accessory devices for control,compensation and safety;

FIG. 7 is a more complete partial sectional view of a hydraulic controlcircuit which also maintains pressure according to another embodiment ofthe invention; and

FIG. 8 represents another variation of the invention in which the sameelastic devices elfect the pressure maintenance of the hydraulic fluidof the control circuit of the breaker as well as the pressuremaintenance of the liquid dielectric.

DETAILED DESCRIPTION Referring to the drawings, the circuit breakershown in FIG. 1 has a cutting chamber 2 in which are arranged, as isnormal, a fixed contact 4 linked to a current feed cable 6, and amovable contact 8 which can slide in a contact jaw 10 linked to acurrent exit cable 12. p

In the embodiment shown the circuit interrupting chamher 2 is mounted onthe top of an insulating column 14 elongated at its lower part by acylinder 16 into which can slide a piston or breaking piston 18. Thispiston is linked to the movable contact 8 by an insulating rod 20 and anintermediate rod 22. The lower face of piston 18 is subject toatmospheric pressure by means of openings 19 in cylinder 16. Fluid-tightjoints are interposed at the junctions between cylinder 16, thediiferent elements of column 14 and the circuit interrupting chamber 2.This latter is surmounted by a fluid-tight compartment 24 supplied witha liquid level 26. The above assembly forms a fluid-tight space, thespace of the circuit interrupting chamber 2 and of compartment 24linking with the space of the insulating column 14, for example, by anopening 3 28. Thus, the movable contact 8 does not need to slide in afluid-tight manner through the bottom 30 of the cutting chamber 2.

The whole of the above space is filled with a dielectric liquid 32 whichis kept permanently under pressure by resilient means comprising in thisembodiment a cushion of gas 34 under pressure (for example air, butpreferably nitrogen) occupying the upper part of compartment 24 andacting directly on the free level 36 of the liquid dielectric.

One end of cylinder 16 is turned towards the movable contact 8 (i.e. theupper end of this cylinder) and communicates with the space filled withpressurized liquid dielectric. This means that the breaking piston 18 ispermanently subject to a force directed downwards and equal to theproduct of the pressure of the dielectric multiplied by the surface ofthe piston, this force tending to push the movable contact 8 from thefixed contact 4 and, as a result, releasing the circuit breaker.

The breaker also comprises, as is normal, releasable interlockingdevices modified to bring and maintain selectively the movable contactagainst the fixed one.

These hydraulic interlocking devices may comprise an interlocking screw38 (pressure cylinder) of which the piston 40 of the plunger pistontype, is linked by translation to the breaking piston 18 by a linkage41. The screw 38 can be selectively supplied with oil under pressure ordrained by a system of hydraulic commutation shown in the drawing by athree-way gate 42. The circuit is completed by a hydraulic accumulator44, for example oleo-pneumatic, fed from a pump 46 which extracts theoil from a tank 48 acting as a draining tank. The three-way gate 42 is aselector valve permitting connection of the pressure cylinder 38 to thehydropneumatic accumulator 44 or to the reservoir 48.

In the interlocked position of the circuit breaker shown in FIG. 1 theoil pressure of accumulator 44 operates in the interlocking screw 38 andholds the moving contact 8 against the fixed contact 4 as long as thegate 42 stays in its feed position shown against the pressure of theliquid dielectric 32 which acts on the operating piston 18.

As soon as the screw 38 is drained by operating gate 42 the pressure ofthe gas cushion 34 transmitted by the liquid dielectric 32 pushes thebreaking piston 18 downwards and separates the movable contact from thefixed one.

In a breaker of the invention an elastic force is always available readyto effect the break, which is an important safety factor, and, inaddition, the harmful phenomena of cavitation when the moving contactwithdraws are considerably reduced or even eliminated due to thepressurizing of the liquid dielectric which feeds with fresh dielectricthe empty space left at the break by the moving contact.

In a breaker of this type, insulating oil for circuit breakers may beused 'as liquid dielectric but it is more advantageous to use aliquified dielectric gas since elastic pressurizing devices are alreadyavailable, which will liquify the gas, and these dielectrics have betterfeatures than oil. Particularly good results are obtained from the gasSF (sulphur hexafluoride), pressurizing being effected by an elasticcushion of gas 34, for example nitrogen, having a higher liquefactionpressure than SP In accordance with the invention the resilientpressurizing devices for the dielectric act both as continuallyavailable breaking devices and as devices for keeping the dielectric gasin the liquid state.

A circuit breaker of the invention can be completed by certain controldevices or safety devices such as: the visible level 26 which allows avisual check on the amount of dielectric (the level of SP being visiblelike a water level); a safety valve 50; a draining valve 52; a fillingvalve '54 which can be used to extract air during installation by meansof nitrogen before the first filling and to elfect the filling with ISF6and nitrogen; and a control device 56 for the pressure of the liquiddielectric.

In a. modification shown in FIG. 2 only the top part of the breaker hasbeen shown, since the lower part with the breaking device can beidentical to that of FIG. 1 or any other standard type.

In this modification the resilient devices for pressuriz ing the liquiddielectric are not pneumatic (such as the cushion of nitrogen 34 inFIG. 1) but mechanical being made up of a spring 58 which acts through alinkage 6062 on a piston 64 sliding in a cylinder 66.

The internal space of the cylinder 66 communicates with the closed space32 of the circuit breaker, this space being entirely filled, right up tothe top 68 of the compartment 24, with liquid dielectric such asliquified SF It is more suitable to arrange cylinder 66 and the spring58 in the lower part of the breaker since this allows, by means of agraduated rod 70 solid with the piston 64, a check on the volume ofliquid dielectric contained in the installation. Due to the choice ofsection of piston 64, the spring 58 need have only a low rate ofdisplacement during the breaking.

Thus a breaker is obtained with breaking by spring but in which theeffort of the spring is transmitted hydraulically without any need formechanical reduction and in which the same spring effects thepressurizing (and in particular the liquifying) of the dielectric.

In the embodiment shown in FIG. 3 the resilient pressurizing devices forthe liquid dielectric comprise, as in FIG. 2, a spring-piston system,but this system is mounted in the upper part of the breaker, since thecylinder 65 in which the piston 64' slides is mounted above the circuitinterrupting chamber 2, i.e., in place of compartment 24 of FIGS. 1 and2. The spring 58' is supported on a fixed flange 72 mounted on the topof the breaker by ties 74, the other end of the spring acting on amovable flange 76 solid in translation with piston 64' due to ties 78, awall-plate 80 and a push rod 62'. As a result of this arrangement aspring 58' of a diameter larger than the bore of cylinder 65 can beused.

In the embodiment shown in FIG. 4 the resilient pressurizing devices actdirectly on the liquid dielectric contained in the circuit interruptingchamber 2, as has been described with reference to FIGS. 1 and 3, butthe communication between the internal space 82 of the circuitinterrupting chamber 2 and the internal space 84 of the insulatingcolumn 14 is no longer by a large communicating orifice such as 28 inthe base 30' of the cutting chamber. This communication is effected by achannel 86 which is bored in the rod of the movable contact 8 and whichopens out at one end into space 82 through the top of the movablecontact and at the other end into space 84 by the orifices 88. Themovable contact slides in fluid-tight manner in the base 30' (or atleast with some clearances of total section lower than the section ofchannel 86) with the result that at breaking an intensive circulation ofliquid dielectric takes place through channel 86 which causes ahydraulic blast of the arc jumping between the end of the moving contactand the fixed contact 4'.

In FIG. 5 is shown a device for regulating the pressure of the liquiddielectric in a breaker of the invention. This device can be applied toany of the preceding embodiments which is why only one part of theinsulating column 14 and one part of the cylinder 16 in which thebreaking piston 18 slides have been shown. One couplesto the space ofthe breaker enclosing the liquid dielectric, for example to the internalspace 84 of insulating column 14, one of the ends of a cylinder 90 inwhich slides a free piston 92 and the other end of which is coupled toan oil hydraulic circuit of constant pressure 93. To sum up, thecompartment 94 of the cylinder 90 contains liquid dielectric underpressure, e.g., liquid SF while compartment 96 contains oil. Circuit 93can comprise a pump 98 driven by an electric motor 100, an oil tank 102and a pressure switch of manostat 104 which is sensitive to the pressurein compartment 96 and whose contacts 106 close to operate motor 100 whenthe pressure falls below a predetermined value P.

If there is a drop in temperature leading to a contraction of the liquidSP or if there is a leak of the SP or, as in the FIG. 1 embodiment, aleak of the gas in the cushion 34, the pressure switch detects a fall inpressure. Below pressure P the pump 98 sends oil into compartment 96until pressure is re-established. In this embodiment the piston-cylindersystem 90-92 serves only to regulate (which can be slow) withoutmotivating the break, which is why the tubing 108 has only a very smallsection compared to that of tubing 66 (FIG. 2) which links cylinder 66with the internal space of the breaker.

If, on the other hand, there is a rise in the pressure of the liquiddielectric caused, say, by a rise in temperature, this increase intemperature is transmitted to the oil compartment 96 and a safety valve109, linked to compartment 96 by channelling -111, drains oif the excessoil to tank 102.

The regulating device above described can be completed by a simplegauging device comprising a cock 110 and a graduated receptacle 112. Byopening cock 110 the oil compartment 96 can be emptied and the quantityof oil therein measured. From this the position of piston 96 and,consequently, the amount of SP can be found. Two cocks 114-116 permitinsulation of pump 100.

FIG. 6 shows another device for compensation and regulation of pressurefor a breaker of the invention.

This device comprises, as in the preceding case, a cylinder 90'separated by a piston in two compartments: one, 94 communicates by apipe 108 with the space 84 of the breaker and the other 96' is coupledto a circuit of oil under constant pressure 93. In this embodiment thepiston 92' is fitted with an exiting rod 118 which is graduated and letsone know the amount of oil and thus the SE; in the installation.

A pressure switch 104 controls, as in the preceding embodiment, theoperation of the motor 100 of the oil pump 98 if the pressure drops but,in the case of excess pressure (for example, following dilation due totemperature rise), the pressure switch closes its contacts 120 toactivate a draining electro-valve 122. The excess oil returns to tank102 by piping 124. A derived piping system 125 into which is fitted acock 127 allows one to link up the oil compartment 96' with tank 102 todrain this compartment, particularly when filling the installation.

FIG. 7 shows an embodiment in which is combined the hydraulicinterlocking control shown in FIG. 1 with the device for compensationand pressure regulation described in connection with FIG. 6.

The hydraulic interlocking control comprises the parts described above,namely, the cylinder 38 and its piston 40, the oleo-pneumaticaccumulator 44, the oil pump 46 and its motor 47, as well as tank 48. Amanostat 104 controls the operation of motor 47 of pump 46 if there is adrop in pressure in accumulator 44.

The three-way cock supply-drain, shown schematically in FIG. 1, isreplaced by an interlocking electro-valve 42' and by an interlockingelectro-valve 42" whose electrical operation will be describedhereinafter.

The piston-cylinder system of compensation device 90- 92' is identicalto that described for FIG. 6, but the oil compartment 96', instead ofbeing fed by a special system of feeding under constant pressure (pump98, motor 100, pressure switch 120) is coupled by piping 126 to thehydraulic control circuit of the breaker. The piping 126 is coupled tothe oil compartment 128 of accumulator 44 by a relief-drainer 130 toreduce the pressure of the hydraulic control circuit to the pressuredesired in chamber 96.

Where the liquid dielectric is liquid SP its pressure can 6 be in theorder of 50 kg./cm. whilst the oil pressure in the hydraulic controlcircuit can be 200 to 300 kg./cm.

The outlet of the relief-drainer is linked by piping 132 to tank 48. Incases of excess pressure in chamber 96 (for example as a result of anincrease in temperature) the oil pushes the piston 134 of drainer 130against the scaled spring 136, which'uncovers a draining orificenormally formed from a clapper valve 138. The oil in excess escapesthrough piping 132.

Activation of the coil of the interlocking electrovalve 42' iscontrolled by an interlocking contact 142 while activation of the coilof the breaking electro-valve 42" is controlled by an interlockingcontact 146. On the valve 42" a contact 148 prevents operation of theinterlocking when the valve is open. As in FIG. 6 piston 92' has a rod118 which permits one to ascertain the volume of dielectric but this rodalso acts as an automatic safety device. Should there be no dielectricin compartment 94 the end 150 of rod 118 closes a contact 152 whichcauses activation of the coil of a relay 154 which automatically closesthe activating circuit 156 of coil 144 of the electrovalve 42".Therefore, below a certain minimal volume of dielectric in the circuitbreaker there is automatic breakmg.

A switch 158 permits manual stopping of the activation of relay 154, andso cancels the order of breaking, to permit the circuit breaker to beput back into service. A general switch 160 completes the installation.

The embodiment shown in FIG. 8 is a variation de rived from theembodiments of FIG. 7 and FIGS. 1 and 2. In this embodiment theresilient pressure device for the dielectric liquid in the circuitbreaker is made up of the cushion of gas 166 of the oleo-pneumaticaccumulator 44, being part of the hydraulic control for the breaker.These resilient devices do not act directly on the dielectric butthrough the intermediary of the oil contained in the oil compartment128, in tubing 168 and in the oil compartment 170 of a cylinder-pistonsystem 162-164 Whose compartment 172 is in communication with theinternal space 84 of the breaker by a large-section tube system 174 likethe tubing 66' of FIG. 2, which permits a large flow.

The cylinder-piston system 162-164 plays the same role as the system64-66 in FIG. 2, i.e., it maintains the pressure of the liquiddielectric and transmits to the breaking piston 18 the energy necessaryfor breaking. In addition, the system 162-164 plays the same role as thesystem 90-92 in FIG. 7, i.e., it ensures compensation for variations involume and pressure of the dielectric.

In this embodiment the adaptation of the high pressure in accumulator 44to the lower pressure of the liquid dielectric is effected, not by areducer (such as reducer 130 in FIG. 7) but by providing the system162-164 with a dilferential piston whose surfaces, turned respectivelyto the oil compartment 170 and the liquid dielectric compartment 172,are in the desired pressure relationship. That is why the rod 118' ofpiston 164 has a larger section than that of rod 118 in FIG. 7. The onlyother modication in respect of the hydraulic or electrical circuitsshown in FIG. 7 lies in the fitting of a safety valve 176 on the oilcircuit to replace the drainer 134-138 incorporated in thereducer-drainer 130 which has been removed.

Described above have been circuit breakers of the type proposed but itwill be appreciated that the invention applies to all types of circuitbreakers and that, in addition, the hydraulic control devices forinterlocking and maintaining locking have been described only by way ofexample. Further, the cylinder and piston for breaking 16-18 can besituated at any point in the breaker other than the one shown as long asthe piston 18 is submitted to the pressure of the liquid dielectric.

I claim:

1. A circuit breaker comprising a circuit interrupting camber containingan insulating liquid, a fixed contact and a movable contact disposed insaid chamber so as to lie within said liquid for all postions of themovable contact relative to the fixed contact, a hydraulicallyoperatedpiston means connected to the movable contact, said piston meanshaving opposite faces, resilient means for continuously producing apressure in the insulating liquid applied through said liquid to oneface of the piston means for urging the latter in a directioncorresponding to the opening stroke of the movable contact, actuatingmeans coupled to the piston means and including a plunger connected tosaid other face of the piston means, a cylinder slidably supporting saidpiston means and a source of liquid under pressure connectable to saidplunger to displace the same and the piston means therewith against theaction of the resilient means, and control means for selectivelyconnecting said plunger to said source of liquid under pressure orexhaust, said cylinder which supports the piston means separating theinsulating liquid and said source of liquid under pressure.

2. A circuit breaker as claimed in claim 1 in which said insulatingliquid is a liquified dielectric gas maintained permanently in theliquid state due to the pressure exerted by the resilient pressurizingmeans.

3. A circuit breaker as claimed in claim 2, in which the liquified gasis a gas having a high extinguishing power.

4. A circuit breaker as claimed in claim 1 in which the resilientpressurizing means for the liquid dielectric is pneumatc, comprising acushion of gas under pressure.

5. A circuit breaker as claimed in claim 1 in which the resilientpressurizing means for the liquid dielectric is a mechanical devicecomprising at least one spring pushing a piston which compresses theliquid dielectric.

6. A circuit breaker as claimed in claim 4 in which the cushion of gasunder pressure acts directly on the free surface of theliquid'dielectric, said cushion being contained in a fluid-tightcompartment which surmounts the circuit interrupting chamber.

the cushion of gas under pressure is a gas having a pressure ofliquefaction higher than that of the liquified dielectric gas fillingthe circuit interrupting chamber.

being in communication, directly or through the intermediary of ahydraulic fluid, with the dielectric of the circuit breaker in order tomaintain it in the liquid state.

9. A circuit breaker as claimed in claim 1 in which the resilientpressurizing means for the dielectric comprises a hydraulic accumulatorof the hydro-pneumatic or spring type.

10. A circuit breaker as claimed in claim 1 in which said source ofliquid under pressure comprises a hydraulic accumulator, the saidaccumulator acting also as a resilient pressurizingdevice for the liquiddielectric.

11. A circuit breaker as claimed in claim 1 in which devices areprovided to control the pressure of said insulating liquid.

12. A circuit breaker as claimed in claim 1 comprising means for controlof the volume of the insulating liquid contained in the circuit breaker.

13. A circuit breaker as claimed in claim 1 in which the movable contactis hollow, the hollow part communicating on one hand with the circuitinterrupting chamber and on the other with a compartment filled withliquid dielectric, as a result of which there is a circulation ofdielectric through the movable contact when this is displaced, thiscirculation directing a flow of liquid dielectric into the zone wherethe arc is formed.

References Cited 7. A circuit breaker as claimed in claim 6, in which 8.A circuit breaker as claimed in claim 7 in which the cushion of gasunder pressure acts on one face of a piston sliding in a cylinder, theother face of this piston UNITED STATES PATENTS 2,850,593 9/1958 Hooveret al. 3,150,245 9/ 1964 Leeds et al. 3,205,331 9/1965 Thommen et al.

' 3,259,724 7/ 1966 Aspey et al.

3,406,269 10/ 1968 Fischer.

FOREIGN PATENTS 430,968 6 1926 Germany.

ROBERTS. MACON, Primary Examiner US. Cl. X.R.

